Shell reaching a very large size, thick and solid, inflated, variable in shape from triangular to hatchet-shaped or sub-globular with a thin wall. Dorsal margin usually nearly straight, posterior margin broadly oval to somewhat truncate in outline, ventral margin broadly convex posteriorly and concave near the umbones, often strongly lobate in medium-sized and large specimens. Outside of valves with 10 to 17 main radial ribs, often bearing scale-like spines, and with weaker interstitial riblets. Internal nacreous layer moderately strong, undivided, occupying the anterior half or 2/3 of valves. Hind margin of posterior adductor scar slightly protruding beyond the nacreous area (protrusion of adductor scar more developed in mature specimens).

Economic Importance and ThreatsImportance: Commercial (The large posterior adductor muscle is highly prized as food, and the black shell carved to make decorative ornaments or plates. Beautiful but very fragile black pearls are sometimes produced by the animal.)

Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at - http://www.marinespecies.org

Samuel, VD; Chacko, D and Edward, JKP (2005) Preliminary study on the molluscan diversity of “the lost world’’– Dhanushkodi, east coast of India Proceedings of the National Seminar on Reef Ecosystem Remediation SDMRI Special Research Publication No.9 54-58 Available at - http://www.sdmri.org/reports/proceedings%202005%20-%20sdmri.pdf

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Available at - www.dkimages.com

Hameed, PS and Somasundaram, SSN (1998) A survey of bivalve molluscs in Gulf of Mannar, India Indian Journal of Fisheries Indian journal of Fisheries for the Indian Council of Agricultural Research, Kochi, India 45(2) 177-181 Available at - http://epubs.icar.org.in/ejournal/index.php/IJF/article/download/8741/3650